Automatic rhythm instrument with beat-dependent tone volume control

ABSTRACT

In an automatic rhythm instrument comprising, a clock pulse generator, cascade arranged multistage counters, a rhythm pattern pulse encoder, rhythm selector switches, a rhythm pattern pulse encoder, rhythm selector switches, rhythm tone generators and a sound reproducing system; the improvement wherein, a beat dependent tone volume control circuit is provided which includes a transistor having its gate or base electrode supplied with any desired output pulse signal from the counter stages and/or the encoder and having its drain-source or emitter-collector path connected in parallel or series to the sound reproducing system so that the volume of rhythm tones emanated from the sound reproducing system varied in response to the pattern of the pulse signal supplied to the gate or base electrode of the transistor acting as a variable impedance element. The sound volumes are selectively changed depending upon the beats of the rhythm performance.

United States Patent [191 Okudaira 11] 3,808,348 Apr. 30, 1974 1 AUTOMATIC RHYTHM INSTRUMENT WITH BEAT-DEPENDENT TONE VOLUME CONTROL Mitsuo Okudaira, l-lamamatsu, Japan Nippon Gakki Seizo Kabushiki Kaisha, Hamamatsu-shi, Shizuoka-ken, Japan Filed: Nov. 22, 1972 Appl. No.: 308,730

[75] Inventor:

[73] Assignee:

[30] Foreign Application Priority Data Nov. 29, 1971 Japan 46-096105 Dec. 6, 1971 Japan 46-098530 References Cited UNITED STATES PATENTS 12/1967 Campbell 84/].03 X

Primary Examiner-Stephen J. Tomsky Assistant Examiner-U. Weldon Attorney, Agent, or Firm-Flynn & Frishauf ABSTRACT In an automatic rhythm instrument comprising, a clock pulse generator, cascade arranged multistage counters, a rhythm pattern pulse encoder, rhythm selector switches, a rhythm pattern pulse encoder,

' rhythm selector switches, rhythm tone generators and a sound reproducing system; the improvement wherein, a beat dependent tone volume control circuit is provided which includes a transistor having its gate or baseelectrode supplied with any desired output pulse signal from the counter stages and/or the encoder and having its drain-source or emitter-collector path connected in parallel or series to the sound reproducing system so that the volume of rhythm tones emanated from the sound reproducing system varied in response to the pattern of the pulse signal supplied to the gate or base electrode of the transistor acting as a variable impedance element. The sound volumes are selectively changed depending upon the beats of the rhythm performance. I

30 Claims, 12 Drawing Figures PATENTEDAPR30 I914 3-L-808L348 SHEET 2 or 9 TO COMMON CONNECTION 2| TO COMMON 20 RI CONNECTION 2| /Rl TO CHANGEOVER X SWITCH 22 MM R2 TO CHANGEOvER R SWITCH 22o HIM-I TO CHANGEOVER TO GROUND OR SWITCH 22b -R22 AMPLIFIER A Q2 TO GROUND OR AMPLIFIER A FIG. 48 2B .TOCOMMON To CQMMON CONNECTION 2| CONNECTION 2| 20| fRl fRl ' TO H NG OV R TO CHANGEOVER NR2 SWI I'C I -I ZZ Q E SWITCH 22 I Q TO CHANGEOVER SWITCH 22b TO GROUND OR AMPLIFIER A TO GROUND OR AMPLIFIER A PATENTED APR 30 I974 SHEET 8 0F 9 m QI AUTOMATIC RHYTHM INSTRUMENT WITH BEAT-DEPENDENT TONE VOLUME CONTROL BACKGROUND OF THE INVENTION This invention relates to an automatic rhythm instrument and more particularly to an automatic rhythm instrument provided with a novel beat-dependent tone volume control. 1

In the conventional automatic rhythm instrument, any desired rhythm sound source or sources are triggered by a preselected one or more of the pulse trains associated with various rhythm patterns such as march, rumba and tango. The triggered rhythm sound sources produce sounds of various percussion instruments (such as a bass drum, snare drum, cymbals, maracas, claves, etc.) or ordinary chord or bass sounds or combinations thereof. Accordingly, rhythm sounds thus produced always have a substantially constant volume. However, natural rhythm instruments like a bass drum, snare drum and cymbals emanate sounds whose volume generally varies continuously, as well as according to the type of said instruments.

Therefore, the prior art automatic rhythm instrument has the drawback that the emanated rhythm sounds present prominent untruthfulness to those obtained from natural musical instruments, causing not only a player but also listeners to-feel the discrepancy.

An electronic musical instrument like an electronic organ which includes an organ section for generating ordinary melody and bass sounds and an automatic rhythm section for producing various' rhythm sounds indeed enables the volume of radiated rhythm sounds to be varied, as is well known, by opration of the'expression pedal. However, the volume control by the expression pedal is not effected automatically, but by a player himself. Moreover, where two or more rhythm SUMMARY OF THE INVENTION An automatic rhythm instrument according to a preferred embodiment of this invention is so designed as to automatically controlthe volumes of musical tones produced by its various rhythm tone generators depending upon the beats in accordance with the patterns of pulse trains associated with any desired rhythm tempo or temposv and/or with the patterns of repetitive pulse trains each having a predetermined frequency or time width to encode the pulse trains associated with said rhythm tempos.

An automatic rhythm instrument of the abovementioned arrangement enables the volumes of reproduced rhythm sounds to be controlled automatically as well as individually.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a schematic circuit arrangement of an automatic rhythm instrument according to an embodiment of this invention;

FIGS. 2A and 2B are different practical circuit arrangements of the automatic tone volume control circuit of FIG. 1;

sounds are emanated, it is difficult to control their vol- FIG. 3 is a schematic circuit arrangement of an automatic rhythm instrument according to another embodiment of the invention;

FIGS. 4A and 4B illustrate different practical circuit arrangements of the automatic tone volume control circuit of FIG. 3;

FIG. 5 is a schematic circuit arrangement of a modification of FIG. 1;

FIG. 6 is a schematic circuit arrangement of a modification of FIG. 3;

FIG. 7 is a schematic circuit arrangement of another modification of FIG. 1;

FIG. 8 is a schematic circuit arrangement of another modification of FIG. 3;

FIG. 9 is a schematic circuit arrangement modified from FIG. 5; and

FIG. 10 is a schematic circuit arrangement modified from FIG. 6.

An automatic rhythm instrument according to the embodiments of this invention and the modifications thereof will now bedescribed by referenceto the appended drawings.

FIG. 1 is a schematic circuit arrangement of an'automatic rhythm instrument according to an embodiment of the invention. Thisautomatic rhythm instrument includes, like the prior art instrument, a free-running oscillation type clock pulse generator 11 such as an astable multivibrator so designed as. to generate a repetitive basic tempo pulse train having a frequency or time width corresponding to the shortest beat unit (e.g. a quaver or a semiquaver) required to synthesize the patterns of pulse trains associated with various rhythm tempos such as waltz, march and rumba; a multistage frequency dividing counter chain for successively ef fecting frequency division upon receipt of output pulses from 'said clock pulse generator 11; a rhythm pattern pulse encoder 13 comprising the known diode matrix, AND logic elements and OR logic elements so as to generate various types of rhythm pattern pulse trains upon receipt of output pulses from the respective stages of said counter chain 12; rhythm selector switches 14 so operated as to permit a player to select before performance any desired rhythm pattern pulse trains encoded by the rhythm pattern pulse encoder 13; a plurality of rhythm sound sources or tone generators S, to S, selectively triggered by preselected rhythm pattern pulse trains passed through the selector switches 14 to produce sounds of various percussion instruments such as a snare drum, bass drum, cymbals, maracas, cleaves,etc. or ordinary chord or bass sounds or combinations thereof; and a sound reproducing system 15 including an amplifier A and a loud-speaker P. In this example, the clock pulse generator 11 has a frequency changing element 16 comprised of a variable resistor.

The counter chain 12 is formed of four stages of binary counters (flip-flop circuits) .12, to 12 each provided with two output lines for generating a pair of output pulses displaced in phase from each other.

The automatic rhythm instrument of this invention basically arranged as described above is further provided with the undermentioned automatic or beatdependent tone volume control circuit 20 so as to give forth through the sound reproducing system 15 any desired rhythm sounds delivered from the triggered one or more of the rhythm tone generators S to S with greatest possible truthfulness to changes in the volumes of rhythm sounds obtained from the corresponding natural rhythm instruments.

This tone volume control circuit 20 comprises a series circuit comprising of a resistor R, and a conduction path or channel formed of the drain-source or emittercollector path of a transistor Q shown in FIG. 2A or 28 connected between ground potential and a common connection 21 to the output lines of the rhythm tone generators S, to S, jointly connected to the input terminal of the amplifier A, namely, in parallel with the sound reproducing system 15; and a resistor R connected parallel with the conduction path or channel of the transistor 0. The gate or base of the transistor Q is connected to the single movable contact of a changeover or selector switch 22 which further includes a plurality of stationary contacts selectively closed by said movable contact. To the stationary contacts are connected any two or more output lines of the aforesaid four stage binary counters 12 to 12., (according to this embodiment, the output lines of the first to third stage counter l2 to 12 and/or the output lines (indicated in dotted lines in FIG. 1) of the rhythm pattern pulse encoder 13 for producing pulse trains associated with various sets of rhythm patterns.

The transistor Q included in the beat-dependent tone volume control circuit 20 is rendered fully conducting when its gate or base is supplied with pulse signals through the changeover switch 22, and becomes nonconducting when there is no supply of said pulse signals. This condition may be reversed, if necessary. With such an arrangement, the transistor acts as a variable impedance element whose internal impedance becomes infinite or zero under control of pulsesignals supplied to the transistor 0 through the changeover switch 22.

According to the automatic rhythm instrument of this invention arranged as described above, the beatdependent tone volume control circuit 20 causes desired rhythm sounds to be given forth from the sound reproducing system 15 with a decreased volume, when the transistor 0 is actuated to have its internal impe dance or resistance reduced substantially to zero under control of pulse signals supplied to the transistor Q through the changeover switch 22. Conversely, when the transistor 0 is not actuated and in consequence has its internal impedance or resistance raised substantially to the infinite value, then said tone volume control circuit causes rhythm sounds to be delivered from the sound reproducing system 15 with an increased volume. Thus, said control circuit 20 effects two-way control. In this case, the difference between the tone volumes obtained is determined by the ratio of resistance which the resistor R, bears to the resistor R, (usually, the output impedance from the preceding stage and the input impedance to the succeeding stage effect the ratio, though). Assuming, for example, that the resistor R, has a resistance 10 times that of the resistor R,, then said difference in the tone volumes will be about 20 dB.

If, therefore, the connection of the movable contact of the changeover switch 22 relative to its plural stationary contacts is previously chosen in accordance with the kind of rhythm sounds delivered from the sound reproducing system 15, then said rhythm sounds can be obtained with as much truthfulness as possible to changes in the volumes of tones emanated from the corresponding natural musical instruments.

Where the movable contact and stationary contacts of the changeover switch 22 are so connected as to selectively derive either of the two output pulses from the first, second or third stages of the binary counter, then the tone volume of 8-, 4- or 2-beat units of each measure (pattern cycle) will be periodically increased or decreased. Further where the movable contact and stationary contacts of the changeover switch 22 are so connected as to selectively drive any of the various rhythm pattern pulse trains from the rhythm pattern pulse encoder 13, then the rhythm sounds delivered from the sound reproducing system 15 will increase or decrease in volume according to the patterns of the preselected rhythm pattern pulse trains, thus permitting the generation of rhythm sounds with widely varying volumes.

Reference numeral 17 in FIG. 1 denotes a feedback switch provided, if necessary, When said switch 17 is closed, the first and second binary counters 12 and 12 will act as a single ternary circuit, thereby changing the rhythm cycle from the 4-beat type based on the period in which the clock pulse generator 11 produces 16 clock pulses per cycle to the 3-beat type based on the period in which twelve clock pulses are generated per cycle. In connection with conversion of counter stages 12 and 12 to a ternary circuit, reference is made to the text Transistor Circuit Engineering," Edited by Richard F. Shea, John Wiley & Sons, 1957, pages 340-344.

In the embodiment of FIG. I, the rhythm sounds obtained have the volumes varied only in two ways. In contrast, a beat-dependent tone volume control circuit 201 of FIG. 3 in which the single transistor 0 of FIG. 1 is replaced by two transistors Q, and 0 provided with conduction paths or channels connected 'in series with each other and having their control electrodes con: nected to the movable contacts of two changeover switches 22a and 22b of the same arrangement as the aforementioned changeover switch 22, enables rhythm sounds to be reproduced with a high volume where both transistors Q, and Q are rendered nonconducting, with a medium volume where either of said transistors Q, and O is made fully conducting, and with a low volume where both transistors Q, and Q, are actuated.

That is, rhythm sounds are reproduced with the volumes varied in three ways. Therefore, the automatic rhythm instrument according to the embodiment of FIG. 3 has the advantage of controlling tone volume with a great variety.

FIG. 5 is a schematic circuit arrangement of a modification of FIG. 1. While, in FIG. 1, the beat-dependent tone volume control circuit 20 is connected parallel with the sound reproducing system 15, said circuit 20 is connected in series therewith in FIG. 5.

FIG. 6 is a modification of FIG. 3 in which the connection of the beat-dependent tone volume control circuit 201 is changed from parallel to series.

The modifications of FIGS. 5 and 6 obviously operate in the same manner as the embodiments of FIGS. 1 and 3, excepting that reversely to FIGS. 1 and 3, rhythm sounds are reproduced with an increased volume where the single transistor or two transistors included in the beat-dependent tone volume control circuit 20 or 201 are rendered fully conducting and with a decreased volume where said transistor or transistors are not actuated.

FIG. 7 is a schematic circuit arrangement of another modification of FIG. 1. In FIG. 1, one sound reproducing system 15 and one beat-dependent tone volume control circuit 20 common to all the rhythm sound sources S, to S, were provided. In the modification of FIG. 7, the rhythm sound sources 5, to S, are divided into a plurality of groups, for example, a first group producing rhythm sounds having relatively high pitches and a second group producing rhythm sounds having relatively low pitches. For each group, one sound reproducing system 15R or 15L and one beat-dependent tone volume control circuit 20R or 20L are provided.

FIG. 8 is a modification of FIG. 3 having the same relationship thereto as that which the modification of FIG. 7 bears to the embodiment of FIG. 1.

FIGS. 9 and 10 are modified from FIGS. 5 and 6. The automatic rhythm instruments arranged as shown in FIGS. 7 to I emanate rhythm sounds whose volumes can be varied to a greater extent than those obtained from the corresponding FIGS. 1, 3, and 6, and further offer the advantage of attaining a sort of stereophonic effect. The parts of FIGS. 3 and 5 to corresponding to those of FIG. 1 are denoted by corresponding numerals, description thereof being omitted.

What is claimed is:

1. In an automatic rhythm instrument comprising a clock pulse generator generating a repetitive pulse train, a multistage frequency dividing. counter chain having a plurality of output lines and being cascade arranged and coupled to said clock pulse generator, a rhythm pattern pulse encoder connected to each stage output of said counter chain and having a plurality of output lines to produce therefrom a plurality of required rhythm pattern pulse trains, rhythm selector switches connected to said encoder, a plurality of rhythm tone generators connected to said rhythm selector switches and each triggered by the preselected one or more of the rhythm pattern pulse trains from said encoder, and at least one sound reproducing system including an amplifier and a loud-speaker and connected together to said rhythm tone generators for making the outputs of the triggered rhythm sound sources audible,

the improvement comprising a tone volume control circuit including: at least one changeover switch having a plurality of stationary contacts connected to at least two of said output lines, said output lines being selected from the output lines of said counter chain and the output lines of said encoder, said changeover switch having a movable contact connected selectively to a selected one of said stationary contacts;

and I at least one active circuit means having a control electrode connected to the movable contact of said changeover switch and having a variable conductivity conduction path coupled in parallel with said sound reproducing system such that the conductivity of said conduction path is controlled by the pattern of pulse signals supplied to said active circuit means through said changeover switch, thereby controlling tone volume. 2. Apparatus according to claim 1 wherein said tone volume control circuit includes a single active circuit means which varies the volume of rhythm sounds emaconnected to the movable contact of said changeover switch, and having a drain and a source, the drainsource path of said field effect transistor comprising said conduction path.

5. Apparatus according to claim 1 wherein said active circuit means comprises a transistor having a base which comprises the control electrode connected to the movable contact of said changeover switch, and having an emitter and a collector, the emitter-collector path of said transistor comprising said conduction path.

6. Apparatus according to claim I further comprising two resistors, one of which is connected in series with the conduction path of said active circuit means and the other of which is connected in parallel therewith.

7. Apparatus according to claim 1 wherein said rhythm tone generators are separated into at least two groups.

8. Apparatus according to claim 7 wherein said sound reproducing system comprises at least two units each being provided in common to said rhythm ton generators constituting each group.

9. Apparatus according to claim 1 wherein said counter chain comprises four stage cascade arranged binary counters.

10. Apparatus according to claim 9 wherein the first and second stages of said binary counters have a feedback loop which is selectively closed, and said first and second stages constituting a single ternary counter when said feedback loop is closed.

11. Apparatus according to claim 3 wherein said at least two active circuit means each comprise a field effect transistor, the drain-source path of said field effect transistor comprising said conduction path of the respective active circuit means.

12. Apparatus according to claim 3 wherein said at least two active circuit means each comprise a transistor, the emitter-collector path of said transistor comprising said conduction path of the respective active circuit means.

13. Apparatus according to claim 1 wherein said stationary contacts of said at least one changeover switch are connected to at least two of the output lines of said counter chain.

14. Apparatus according to claim 1 wherein said stationary contacts of said at least one changeover switch are connected to at least two of said output lines of said encoder.

15. Apparatus according to claim I wherein said stationary contacts of said at least one changeover switch are connected to at least one output line of said counter chain and to at least one output line of said encoder.

16. In an automatic rhythm instrument comprising a clock pulse generator generating a repetitive pulse train, a multistage frequency dividing counter chain having a plurality of output lines andbeing cascade arranged and coupled to said clock pulse generator, a rhythm pattern pulse encoder connected to each stage output of said counter chain and having a plurality of output lines to produce therefrom a plurality of required rhythm pattern pulse trains, rhythm selector switches connected to said encoder, a plurality of rhythm tone generators connected to said rhythm selector switches and each triggered by the preselected one or more of the rhythm pattern pulse trains from said encoder, and at least one sound reproducing system including an amplifier and a loud-speaker and connected together to said rhythm tone generators for making the outputs of the triggered rhythm sound sources audible,

the improvement comprising a tone volume control circuit including:

at least one changeover switch having a plurality of stationary contacts connected to at least two of said output lines, said output lines being selected from the output lines of said counter chain and the output lines of said encoder, said changeover switch having a movable contact connected selectively to a selected one of said stationary contacts; and

at least one active circuit means having a control electrode connected to the movable contact of said changeover switch and having a variable conductivity conduction path coupled in series between said rhythm tone generators and said sound reproducing system such that the conductivity of said conduction path is controlled by the pattern of pulse signals supplied to said active circuit means through said changeover switch, thereby controlling tone volume.

17. Apparatus according to claim 16 wherein said tone volume control circuit includes a single active circuit means which varies the volume of rhythm sounds emanated from said sound reproducing system in two different patterns.

18. Apparatus according to claim 16 wherein said tone volume control circuit includes at least two active circuit means connected in series with each other and varying the volume of rhythm sounds emanated from said sound reproducing system in at least three different patterns.

19. Apparatus according to claim 16 wherein said active circuit means comprises a field effect transistor having a gate which comprises the control electrode connected to the movable contact of said changeover switch, and having a drain and a source, the drainsource path of said field effect transistor comprising said conduction path.

20. Apparatus according to claim 16 wherein said active circuit means comprises a transistor having a base which comprises the control electrode connected to the movable contact of said changeover switch, and having an emitter and a collector, the emitter-collector path of said transistor comprising said conduction path.

21. Apparatus according to claim 16 further comprising two resistors, one of which is connected in series with the conduction path of said active circuit means and the other of which is connected in parallel therewith.

22. Apparatus according to claim 16 wherein said rhythm tone generators are separated into at least two groups.

23. Apparatus according to claim 22 wherein said sound reproducing system comprises at least two units each being provided in common to said rhythm tone generators constituting each group.

24. Apparatus according to claim 16 wherein said counter chain comprises four stage cascade arranged binary counters.

25. Apparatus according to claim 16 wherein the first and second stages of said binary counters have a feedback loop which is selectively closed, said first and second stages constituting a single ternary counter when said feedback loop is closed.

26. Apparatus according to claim 18 wherein said at least two active circuit means each comprise a field effect transistor, the drain-source path of said field effect transistor comprising said conduction path of the respective active circuit means.

27. Apparatus according to claim 18 wherein said at least two active circuit means each comprise a transistor, the emitter-collector path of said transistor comprising said conduction path of the respective active circuit means.

28. Apparatus according to claim 16 wherein said stationary contacts of said at least one changeover switch are connected to at least two of the output lines of said counter chain.

29. Apparatus according to claim 16 wherein said stationary contacts of said at least one changeover switch are connected to at least two of said output lines of said encoder.

30. Apparatus according to claim 16 wherein said stationary contacts of said at least one changeover switch are connected to at least one output line of said counter chain and to at least one output line of said encoder. 

1. In an automatic rhythm instrument comprising a clock pulse generator generating a repetitive pulse train, a multistage frequency dividing counter chain having a plurality of output lines and being cascade arranged and coupled to said clock pulse generator, a rhythm pattern pulse encoder connected to each stage output of said counter chain and having a plurality of output lines to produce therefrom a plurality of required rhythm pattern pulse trains, rhythm selector switches connected to said encoder, a plurality of rhythm tone generators connected to said rhythm selector switches and each triggered by the preselected one or more of the rhythm pattern pulse trains from said encoder, and at least one sound reproducing system including an amplifier and a loud-speaker and connected together to said rhythm tone generators for making the outputs of the triggered rhythm sound sources audible, the improvement comprising a tone volume control circuit including: at least one changeover switch having a plurality of stationary contacts connected to at least two of said output lines, said output lines being selected from the output lines of said counter chain and the output lines of said encoder, said changeover switch having a movable contact connected selectively to a selected one of said stationary contacts; and at least one active circuit means having a control electrode connected to the movable contact of said changeover switch and having a variable conductivity conduction path coupled in parallel with said sound reproducing system such that the conductivity of said conduction path is controlled by the pattern of pulse signals supplied to said active circuit means through said changeover switch, thereby controlling tone volume.
 2. Apparatus according to claim 1 wherein said tone volume control circuit includes a single active circuit means which varies the volume of rhythm sounds emanated from said sound reproducing system in two different patterns.
 3. Apparatus according to claim 1 wherein said tone volume control circuit includes at least two active circuit means connected in series with each other and varying the volume of rhythm sounds emanated from said sound reproducing system in at least three different patterns.
 4. Apparatus according to claim 1 wherein said active circuit means comprises a field effect transistor having a gate which comprises the control electrode connected to the movable contact of said changeover switch, and having a drain and a source, the drain-source path of said field effect transistor comprising said conduction path.
 5. Apparatus according to claim 1 wherein said active circuit means comprises a transistor having a base which comprises the control electrode connected to the movable contact of said changeover switch, and having an emitter and a collector, the emitter-collector path of said transistor comprising said conduction path.
 6. Apparatus according to claim 1 further comprising two resistors, one of which is connected in series with the conduction path of said active circuit means and the other of which is connected in parallel therewith.
 7. Apparatus according to claim 1 wherein said rhythm tone generators are separated into at least two groups.
 8. Apparatus according to claim 7 wherein said sound reproducing system comprises at least two units each being provided in common to said rhythm tone generators constituting each group.
 9. Apparatus according to claim 1 wherein said counter chain comprises four stage cascade arranged binary counters.
 10. Apparatus according to claim 9 wherein the first and second stages of said binary counters have a feedback loop which is selectively closed, and said first and second stages constituting a single ternary counter when said feedback loop is closed.
 11. AppaRatus according to claim 3 wherein said at least two active circuit means each comprise a field effect transistor, the drain-source path of said field effect transistor comprising said conduction path of the respective active circuit means.
 12. Apparatus according to claim 3 wherein said at least two active circuit means each comprise a transistor, the emitter-collector path of said transistor comprising said conduction path of the respective active circuit means.
 13. Apparatus according to claim 1 wherein said stationary contacts of said at least one changeover switch are connected to at least two of the output lines of said counter chain.
 14. Apparatus according to claim 1 wherein said stationary contacts of said at least one changeover switch are connected to at least two of said output lines of said encoder.
 15. Apparatus according to claim 1 wherein said stationary contacts of said at least one changeover switch are connected to at least one output line of said counter chain and to at least one output line of said encoder.
 16. In an automatic rhythm instrument comprising a clock pulse generator generating a repetitive pulse train, a multistage frequency dividing counter chain having a plurality of output lines and being cascade arranged and coupled to said clock pulse generator, a rhythm pattern pulse encoder connected to each stage output of said counter chain and having a plurality of output lines to produce therefrom a plurality of required rhythm pattern pulse trains, rhythm selector switches connected to said encoder, a plurality of rhythm tone generators connected to said rhythm selector switches and each triggered by the preselected one or more of the rhythm pattern pulse trains from said encoder, and at least one sound reproducing system including an amplifier and a loud-speaker and connected together to said rhythm tone generators for making the outputs of the triggered rhythm sound sources audible, the improvement comprising a tone volume control circuit including: at least one changeover switch having a plurality of stationary contacts connected to at least two of said output lines, said output lines being selected from the output lines of said counter chain and the output lines of said encoder, said changeover switch having a movable contact connected selectively to a selected one of said stationary contacts; and at least one active circuit means having a control electrode connected to the movable contact of said changeover switch and having a variable conductivity conduction path coupled in series between said rhythm tone generators and said sound reproducing system such that the conductivity of said conduction path is controlled by the pattern of pulse signals supplied to said active circuit means through said changeover switch, thereby controlling tone volume.
 17. Apparatus according to claim 16 wherein said tone volume control circuit includes a single active circuit means which varies the volume of rhythm sounds emanated from said sound reproducing system in two different patterns.
 18. Apparatus according to claim 16 wherein said tone volume control circuit includes at least two active circuit means connected in series with each other and varying the volume of rhythm sounds emanated from said sound reproducing system in at least three different patterns.
 19. Apparatus according to claim 16 wherein said active circuit means comprises a field effect transistor having a gate which comprises the control electrode connected to the movable contact of said changeover switch, and having a drain and a source, the drain-source path of said field effect transistor comprising said conduction path.
 20. Apparatus according to claim 16 wherein said active circuit means comprises a transistor having a base which comprises the control electrode connected to the movable contact of said changeover switch, and having an emitter and a collector, the emitter-collector path of said transistor comprising said conduction path.
 21. Apparatus according to claim 16 further comprising two resistors, one of which is connected in series with the conduction path of said active circuit means and the other of which is connected in parallel therewith.
 22. Apparatus according to claim 16 wherein said rhythm tone generators are separated into at least two groups.
 23. Apparatus according to claim 22 wherein said sound reproducing system comprises at least two units each being provided in common to said rhythm tone generators constituting each group.
 24. Apparatus according to claim 16 wherein said counter chain comprises four stage cascade arranged binary counters.
 25. Apparatus according to claim 16 wherein the first and second stages of said binary counters have a feedback loop which is selectively closed, said first and second stages constituting a single ternary counter when said feedback loop is closed.
 26. Apparatus according to claim 18 wherein said at least two active circuit means each comprise a field effect transistor, the drain-source path of said field effect transistor comprising said conduction path of the respective active circuit means.
 27. Apparatus according to claim 18 wherein said at least two active circuit means each comprise a transistor, the emitter-collector path of said transistor comprising said conduction path of the respective active circuit means.
 28. Apparatus according to claim 16 wherein said stationary contacts of said at least one changeover switch are connected to at least two of the output lines of said counter chain.
 29. Apparatus according to claim 16 wherein said stationary contacts of said at least one changeover switch are connected to at least two of said output lines of said encoder.
 30. Apparatus according to claim 16 wherein said stationary contacts of said at least one changeover switch are connected to at least one output line of said counter chain and to at least one output line of said encoder. 